岩墙厚度对成矿作用的约束:以石湖金矿为例  

Constraints of dike thicknesses on the metallogenesis and its application to the Shihu gold deposit

作　　者：李德东[1] 罗照华[1] 周久龙[1] 杨宗锋[1] 刘翠[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083

出　　处：《地学前缘》2011年第1期166-178,共13页Earth Science Frontiers

基　　金：国家自然科学基金项目(90814007);中俄合作基金项目(40911120079;RFBR-GFEN08-05-92224);中国地质调查局地质调查工作项目(1212010911028)

摘　　要：根据透岩浆流体成矿理论,岩浆体是含矿流体的通道而不是来源,因而估算含矿流体注入岩浆体的能力是评价高位侵入体成矿潜力的有效方法。文中利用一维传热模型计算了石湖金矿区三类代表性岩墙(花岗斑岩、石英闪长玢岩和辉绿岩)不同厚度条件下的冷却时间尺度,同时估算了岩浆冷却过程中的粘度变化速率。假定岩浆侵位于约6 km,且完全固结时含矿流体才不能有效注入,石湖金矿区三类代表性岩墙的最小临界成矿厚度分别为33.45 m(花岗斑岩)、8.22 m(石英闪长玢岩)和1.02 m(辉绿岩)。模拟结果与石湖金矿区矿体的产状一致,暗示模拟结果具有较强的实用价值。结合岩墙长度/宽度比值,进一步估算致矿侵入体的最小临界出露面积分别约为312～1 561 m2(玄武质岩体)、0.014～0.068 km2(石英闪长玢岩)和0.011～0.034m2(花岗斑岩)。估算结果为野外地质找矿提供了一个定性的标准,对快速资源勘查具有参考价值。According to the metallogenic theory of the transmagmatic fluids,the magma body is not the source of ore-bearing fluids,but the channel for the fluids.Thus,it will be an effective way to estimate the ore forming potential by calculating the content of fluids injected into the magma body.One-dimensional heat transfer model is used to calculate the cooling time with different thicknesses of three representative types of dikes（granite porphyry,quartz diorite and diabase） in Shihu gold mine.The change rate of magma viscosity during the cooling is also estimated.Assuming that these magmas have been emplaced at ～6 km depth and that the ore-bearing fluid could not be effectively injected into the magma body only after these magmas were fully crystallized,we obtained the minimum critical thickness of mineralization of three representative types of dikes as follows： 33.45 m for granite porphyry,8.22 m for quartz diorite and 1.02 m for diabase in Shihu gold mine.Simulation results are consistent with the occurrence of ore bodies,suggesting that they are of practical value.According to the length/width ratio of the dike,the minimal critical ore-forming intrusion outcrop area is estimated： 312-1561 m2 for diabase,0.014-0.068 km2 for quartz diorite and 0.011-0.034 km2 for granite porphyry.This kind of estimation provides a qualitative standard for field geological prospecting,and has certain reference value for rapid exploration.

关 键 词：岩墙 冷却时间 数值模拟 高位侵入体 临界厚度 石湖金矿 透岩浆流体 

分 类 号：P588.12[天文地球—岩石学]